Summarizing The Global Positioning System

Summarizing The Global Positioning

System

Abstract:Global Positioning System is based on the background of the United States Department of Defense.It is designed,invested,developed,and operated by the United States Department of Defense ,GPS is a satellite-based positioning and time transferingGPS positioning function has awide range of applications in the modern measurement and a more modern building.GPS-RTK technologyis also widely used in modernization building, and now GPS has also been shown to be an important civilian communities of interest, andincreasingly wide range of applicated.

Keywords:GPS; Locating; RTK; Lay out; Survey

1.Background

The 50s, the former U.S.S.R has not launched humanities first artificial earth satellite, the American scientists in along its track research in, had discovered the Doppler shift phenomenon, and has facilitated Doppler satellite navigation posi- tioning system completing using this principle, has obtained the enormous success in the military and the civi aspect, was in a navigation localization history leap, our country once has also introduced many Doppler receiver, applied to the island association measured, the Earth explored and so on the applied to the island association measured, the Earth explored and so on the domain. But because Doppler satellite orbit highly low, signal-carrier frequency low, the track precision enhances with difficulty, causes the pointing accuracy lowly, satisfies the geodetic survey or the project survey request, is more impossible to use in the astronomy Earth

dynamics research. In order to enhance the satellite positioning the precision,US started from 1973 to prepare for construction global positioning system GPS (Global Positioning System).After has entered the plan proof, the system test stage,started in 1989 to launch the official work satellite,and completely completed in 1994, investment use. The GPS system spaceartially is composed by twenty one satellites, evenly distributes in six orbit, the ground level is 20,000 Kilometers, the inclination of orbit is 55, the flat heart rate approximately is 0, the week contract is 12 hours, the satellite to the earth launching two wave bands intelligence signals,the intelligence signal frequency respectively is 1575.442 mega cycles per second (the L2 wave band), on the satellite has installed the precision very high atomic clock, guarantees the frequency the stability, modulates in the carrier has the expression satellite position the broadcast star experience, use in the range finder C/A code and P yard, as well ad other system information, can in the global scope, to willfully multi-user provide the high accuracy, all-weather, is continual, real-time three dimensional measures fast, the three dimensional localization and the time service.

The GPS system control section by is located in the American foundations of the states 5 monitoring stations to be composed, these stand did not ask breaks Carries on the observation to GPS satellite, and will calculate and the forecast information by the infusion stands renews to the satellite information.

The GPS system user is extremely covert, it is one kind of one-way system,the user only receives but does not need the transmitting message, and therefore user' s quantity also is not limited. Although GPS is the unification starts is, but very quantity also is not limited. Although GPS

receiver and processing software emerge in abundance. At present the receiver which appears in the Chinese market mainly has ROGUE,ASHTECH, TRIMBLE, LEICA, SOKKIA, TOPCON and so on.. Can carry on the observation to two frequencies the receiver to be called the double frequency receiver, only can carryon the observation to a frequency the receiver to become the inference. Says regarding the mapping user, GPS has caused the revolutionary change in the mapping domain, at present, in the scope several thousand kilometers controls network, in the precision from hundred to the millimeter level localization, generally all GPS took the first choice method, is day by day mature along with the RTK technology, GPS started to decimeter and even a centimeter level layout, domain seepage and so on high accuracy dynamic localization.

The international GPS geodetic survey served IGS with Earth dynamics from 1992, has established many data storage and the processing center in the whole world, year to year observed a station with hundred, our country has also set up Shanghai Yu Shan, Wuhan, Xian, Taiwan and so on many year to year measuring platforms station, these stations observation data passed on every day through the internet net to US' S data storage center, IGS also nearly real-time synthesizes various data processing center the result, and the participant international earth rotation served the IERS global coordinates reference system maintenance and the earth rotation parameter issue. The user also may free on-line obtain product and so on observation data and precise star experience from internet.

The GPS system real-time navigation pointing is very high,UShasimplemented the so-called SA policy in 1992, namely reduces the broadcaststar to undergo the star position precision, reduces the star clock to

change thepositive number the precision, adds on the high frequency vibration to thesatellite datum frequency (to cause false distance measuring accuracy to reducewith phase ), latter has implemented the A-S policy, soon P yard change is Y yardnamely further limits to the precise false distance survey, but American military and special permission user not these polices influences, but US in order to obtain the bigger commercial interest, these policy ends are cancelled.

2.GPS localization principal

The GPS receiver may receive and use in the time service accurately to the nanosecond level time information; will use in to forecast the future for several months the satellite to locate the summary position forecast star experience; Uses in calculates when the localization to need the satellite coordinates the broadcast star experience, the precision is (each satellite is different several meter to several dozensmeters~changes as necessary); As well as GPS system information, like satellite condition and so on.

The GPS receiver may obtain the satellite sign to the code to the receiver distance, because includes the receiver satellite clock the error and the atmosphere propagated error, therefore is called the false distance. The false distance obtains which to the OA code is called the UA code false distance, the precision approximately is about 20 meters, obtains the false distance to P yard to be called P yard false distance, the precision approximately is about 2 meters.

The GPS receiver to the satellite signal which receives, carries on the decoding or uses other technologies, will modulate after the carrier the information removes, will be allowed to restore the carrier. Strict says, the

carrier phase should be called the carrier beat frequency phase, it is receives produces the Doppler shift influence satellite signal carrier phase and receiver this machine vibration difference of the signal phase. Generally experience Yuan time which determined in the receiver clock surveyed, maintains to the satellite signal track under, may record the phase change value, but starts time the observation receiver and the satellite oscillator phase change value is does not know, namely misty degree of whole week, only can calculate in the data processing as the parameter solution. Phase observation value precision high to millimeter, but the premise is solves misty degree of whole week, therefore only has when the relative localization, and has a section continuously observes the value can use the phase observation value, but must achieve meters down to themillimeter level also only to be able to use the phase observation value.

According to the locate mode, the GPS localization divides into the simple point localization and the relative localization (difference localization). The simple point localization is according to a receiver observation data determined the receiver position the way, it only can use the false distance view survey, may use in Chef Chuan and so on the summary navigation localization. The relative localization (difference localization) is according to two above receivers observation data determined between the observation point the relative position method, it already may use the false distance view survey also to be possible to use the phase view survey, the geodetic surveyor the project survey should use the phase observation value to carryon the relative localization. Has contained the satellite and receiver ZhongChai, the atmospheric dissemination in the GPS view survey retards, error and so on multipart effect, when localization error the influence, when carries on the

relative localization the majority of public errors are counterbalanced or weaken, therefore the pointing accuracy greatly will enhance, the double frequency receiver will be allowed to act according to two frequencies in the view survey counterbalance atmosphere the ionosphere-path error main part, will request high in the precision, between the receiver the distance wi11 be farther when (atmosphere will have obvious difference), will be supposed to select the double frequency receiver.

When localization observation, if the receiver is opposite to the earths surface movement, then is called the dynamic localization, like uses in summary navigation localization the and so on Chef Chuan precision is 30-100 meter false distance simple point localization, either uses in the city vehicles navigation localization rice level precision false distance difference localization(RTK), the real-time difference localization needs the data chain real-time transmits two or many stations observation data calculates together.

When localization observation, if the receiver is opposite to the earths surface static, then is called the static localization, when carries on controls the net observes, generally selects this method by several receivers also to observe, it can maximum limit display GPS the pointing accuracy,special-purpose Yu Zheizhong the goal receiver is called the earth receiver,is in the receiver a performance best kind. At present, GPS already could achieve the earths crust performance observation the precision request, IGS year to year the measuring platform already can constitute millimeter level the global coordinates frame.

3.RTK technologies

The conventional GPS measuring technique, like the static state, the

faststatic state , the dynamic survey all~eed afterwards to carryon the solution tocalculate can obtain a centimeter level the precision, but RTK is can real-timeobtain the centimeter level pointing accuracy in the open country themeasuring technique, it has used the carrier phase dynamic real-timedifference (Real-timekinematics) the method, is the GPS application significantmilestone, its appearance for the project layout, the terrain mapping, each kind ofcontrol survey has brought the new dawn, enormously enhanced the fieldoperation work efficiency.

The high accuracy GPS survey must use the carrier phase observation value,the RTK localization technology, it can real-time provide in assigns in thecoordinate system the three dimensional localization result, and achievesthe centimeter level precision. Under the RTK work pattern, the datum standsthrough the data chain transmits together its observation value and the surveystation coordinates information for the mobile station. Mobile standsnot only receives the data through the data link which stands from thedatum, but also must gather the GPS observation data, and composes thedifference observation value in the system to carryon the real-time processing,simultaneously produces the centimeter level localization result, a lasted. Themobile station may be at the static condition, also may be at the state of motion;May first carryon the initialization after the fixed point to enter the dynamicwork again, also may under the dynamic condition directly opening machine,and completes the week fuzziness search solution under the dynamicenvironment. After end knows the number solution to be fixed, then carries oneach calendar Yuan real-time processing, so long as can maintain four abovesatellites phases observation value the track and the essential geometric figure,then the mobile station may produce the centimeter level

localization result asnecessary.

The RTK technology key lies in the data processing technology and the datatransmission technology, when the RTK localization requests the datum stationreceiver real-time the observation data (false distance observation value, phaseobservation value) and the know data transmission for the mobile station receive,the data quantity quite big, generally all requests 9,600 bauds rate, this in onradio is not difficult to realize.

4.The application of RTK

(1)Each kind of control survey

The traditional geodetic survey, the project control survey uses the triangular net, the line-network method executes measured, not only requires a lot of work time-consuming, request Indivisibility, moreover the precision distribution non-uniformity, also at the field operation did not know how the precision, does use conventional the GPS static state survey, the fast static state, the false dynamic method, survey in the process at field operation not to be able real-time to know the pointing accuracy, after if surveys completes, after returns to house processing to discover the precision does no t gather the request, but also must return measured, but uses RTK to carryon the control survey, can real-time know the pointing accuracy, if the fruits and cakes position precision request has satisfied, the user was allowed to stop observing, how moreover knew the observation quality, This may greatly enhance the work efficiency. If uses in the road control survey RTK,electronic circuit control survey, the hydraulic engineering control survey, the geodetic survey, then not only may greatly reducethe manpower intensi ty, the economical expense, moreover greatly enhances the working

efficiency,measured a control point may complete in several minutes even several seconds.

(2)Terrain mapping

In the past measured when topographic diagram generally first must in measure area establishment chart root control point, then on chart root control point top carriage entire station meter or altazimuth coordination small flat panel mapping, now develops the field operation with the entire station meter and the electronic hand coordination thing code, uses big scale mapping software to carryon the mapping, even develops recent field operation electron dull mapping and so on, all requests in the survey station to measure all around terrain landform and so on department point, these points all with survey station indivisibility, moreover generally requests at least 2-3 person to operate, needs when puts together the chart once the precision not to gather the request also to obtain the field operation to return measured,when now uses RTK, only needs a person to carry the instrument in on the terrain landform department point dull 12 second kinds which must measure, and simultaneously inputs the characteristic code, through hand book may real-time know the position precision, after measured a region returns to in the room, may output the topographic diagram by the specialized software connection which requests, like this uses RTK only to need a person to operate,does not request a between indivisibi Ii ty, greatly enhanced the working efficiency, uses the RTK coordination electron hand book to be allowed to survey each kind of topographic diagram, I ike the ordinary mapping, the track，line strip the shape topographic diagram surveying, road pipeline topographic diagram surveying, coordinates the depth-finding device to be allowed to use in to measure the reservoir

topographic diagram, Navigation sea mapping and so on.

(3)Layout

Layout surveys an application branch, it request through the certain method to use the certain instrument the spot position which artificial designs in really for to demarcate, in the past used the convention layout the method very many, like the altazimuth junction met layout, when the ent ire 50 station meter and so on, generally layout a design position, often needed the back and forth bile target, moreover took 2-3 person to operate, simultaneously also requested the indivisibility situation in the process to be good, in the production application the efficiency was not very high, sometimes layout encountered the difficult situation to be able to draw support fromYu Hindu the method to layout. Sometimes, if uses the RTK technology layout, only must the spot position coordinates which designs input to the electron hand, is carrying the GPS receiver, it can remind you to walk to want to layout a position, both rapid and convenient, because GPS is comes directly through the coordinates layout,the precision is very high, thus can greatly enhance efficiency, also only needs a person to operate.

5. The application of GPS

GPS offers for military and makes a reservation and sets up accurately atfirst, it is still controlled by the American military so far. Military GPS productsis it confirm and follow in field advancing soldering and coordinating ofequipment in to used for mainly, the gunship for the sea navigates, offersthe position and navigation information for military aircraft.

(1) The GPS system use is extensively

At present, application, GPS of system very extensive already, we can useGPS

signal can carryon sea, empty and navigation of land, the guidance of theguided missile, earth measurement and accurate localization of projectmeasurement., transmission of time and measurement of the speed,etc.Forsurvey and drawfield,GPS satellite fix technology is it set up nationwide earthmeasurement of high accuracy control network to use for already, determineglobal dynamic parameter of earth;Used for setting up land marine earthmeasurement datum, unite and examines and surveys and draws in the ocean thehigh-accuracy island land;Used for monitoring plate motion state of the earthand the earths crust deformation;Used in project measure,is it set up city andproject control main means of network to become For determine Aero-Spacephotograph camera position in the twinkling of an eye, realize for a smallamount of ground control or there is no aerial survey controlled in region tobecome and pursue fast, technical revolution causing the geographicalinformation system,global environmental remote to follow their monitor.A lotof commerce andgovernment organs use GPS equipment to follow their vehicleposition;This generally needs to draw support from wireless communicationtechnology.Some GPS receiver integrated radio, radio telephone move dataterminal is it meets need, motorcade of management to come.

(2) Appearance of the resource environment of pluralistic space

At present, GPS, GLONASS, INMARSAT waits for the system to all possessand navigate to orient the function, formed the pluralistic room resourceenvironment. This pluralistic space environment ,has impelled and fumed a pieceof common tactics internationally and folly, namely on one hand fully utilize theexisting system, on the other hand prepare to establish folk GNSS systemactively ,by the tome around the2010,GNSS folk system build our purely, thewoke world form the tendency that

GPS/GLONASS/GNSS stood like the legs ofa tripod, could get rid of the reliance on the single system fundamentally, formowning in common, security resource environment which world shares ofworlk.World can is it is it use realm at most as single navigation means tonavigate satellite to enter. This international and folk strategy, there id influenceand force U.S.A to use the policy to make more omen adjustment to its GPSconverselu. Inaword , because of the establishment of the resource environmentof pluralistic space ,have created an unprecedented gapped internationalenvironment for the development and application of GPS.

(3) Develop gaps industry

GPS Will form industrialization like the automobile, wirelesscommunication at present in the future, US>A strengthen wide area systematicWAAS (namely wide area is it revise date chain transfer to already, it makegeostationary satellite it have C? A yards of function too, form wide area theGPS strengthen system of) plan international standard of developing intoof.Some units produce car-mounted GPS system too at present in our country.For GPS industry of developing our country, already China GPS project centrehas been established in Wuhan.